Control of Uplink Radio Transmissions on Semi-Persistently Allocated Resources

ABSTRACT

A radio device receives control information from a node of the wireless communication network. The control information is used for controlling semi-persistent allocation of radio resources of an unlicensed frequency spectrum. Based on the control information, the radio device controls at least one UL radio transmission on the radio resources of the unlicensed frequency spectrum.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/229,323, filed Apr. 13, 2021, which is a continuation of U.S. patentapplication Ser. No. 16/492,968, filed Sep. 11, 2019, now U.S. Pat. No.11,019,651, which is a national stage application of PCT/EP2017/084049,filed Dec. 21, 2017, which claims benefit of U.S. ProvisionalApplication No. 62/476,089, filed Mar. 24, 2017, the disclosures of eachof which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to methods for controlling radiotransmissions in a wireless communication network and to correspondingdevices and systems.

BACKGROUND

Wireless communication networks, such as wireless communication networksbased on the LTE (Long Term Evolution) technology specified by 3GPP (3rdGeneration Partnership Project), typically operate in a licensedfrequency spectrum, i.e., on frequency resources which are dedicated toa certain radio technology and operator. Further, also the utilizationof radio resources from an unlicensed frequency spectrum, e.g., in the 5GHz or 3.5 GHz frequency band, may be possible. Typically, radioresources from such unlicensed frequency spectrum are shared withanother operator or one or more other radio technologies. The unlicensedspectrum is used as a complement to the licensed spectrum or allowscompletely standalone operation.

In the LTE technology radio resources from an unlicensed frequencyspectrum may be utilized on the basis of a technology referred to as“Licensed-Assisted Access” (LAA). Aspects of the LAA technology arediscussed in 3GPP TR 36.889 V13.0.0 (2015-06). In the LAA technology theunlicensed spectrum is used as a complement to the licensed spectrum.Using carriers from the licensed spectrum, a UE (user equipment)connects to the network. The carriers from the licensed spectrum arealso referred to as primary cell or PCell. In addition one or moreadditional carriers, referred to as secondary cell or SCell, from theunlicensed spectrum are used to enhance transmission capacity. For thispurpose, a carrier aggregation functionality of the LTE technology isutilized. The carrier aggregation functionality allows to aggregate twoor more carriers, i.e., frequency channels. In a typical LAA scenario,at least one of the aggregated carriers is from the licensed spectrumand at least one of the aggregated carriers is from the unlicensedspectrum.

Due to regulatory requirements, transmissions in the unlicensed spectrumare typically permitted only with prior channel sensing, transmissionpower limitations, and/or imposed maximum channel occupancy time. Totake into account that the radio resources from the unlicensed spectrumare shared with other operators or other radio technologies, an LBT(listen-before-talk) procedure may be needed to perform beforeproceeding to a transmission in the unlicensed spectrum. Typically, theLBT procedure involves sensing the carrier for a pre-defined minimumamount of time and backing off if the carrier is busy. If on the otherhand the transmissions on the radio resources are coordinated in acentralized manner, like by dynamic scheduling as used in the LTEtechnology, performance may be significantly degraded because situationsmay occur where the centralized scheduling may grant a transmission, butthe transmission is not possible because the carrier is busy, orsituations may occur where the carrier would be free, but a transmissionwas not granted by the centralized scheduling. In the case of the LAAtechnology, this may for example effect the performance of uplink (UL)transmissions from the UE to the network. However, good performance forthe UL transmissions is becoming more relevant, e.g., due to increasingusage of user-centric applications and an increasing need to push datato cloud storage.

A degradation of performance when using the LTE technology in theunlicensed spectrum may also arise from unfair competition with otherradio technologies. For example, the unlicensed 5 GHz band is currentlymainly used by WLAN (Wireless Local Area Network) communicationaccording to the IEEE 802.11 standard family. According to thesestandards, a device can asynchronously access a given frequency channel,without requiring any centralized coordination. As compared to the LTEtechnology, which uses centralized scheduling, this increases thechances of gaining access to the frequency channel, in particular incongested network conditions. Accordingly, a UE which tries to gainaccess to a certain carrier from the unlicensed spectrum for an LAAbased UL transmission will have less chances to gain access to thecarrier than a WLAN device operating on a frequency channel which atleast partially overlaps with this carrier.

Accordingly, there is a need for techniques which allow for efficientcontrol of UL radio transmissions in an unlicensed spectrum.

SUMMARY

According to an embodiment of the invention, a method of controllingradio transmission in a wireless communication network is provided.According to the method, a radio device receives, from a node of thewireless communication network, control information for semi-persistentallocation of radio resources of an unlicensed frequency spectrum. Basedon the control information, the radio device controls at least one ULradio transmission on the radio resources of the unlicensed frequencyspectrum.

According to a further embodiment of the invention, a method ofcontrolling radio transmission in a wireless communication network isprovided. According to the method, a node of the wireless communicationnetwork semi-persistently allocates radio resources of an unlicensedfrequency spectrum to a radio device. Further, the node sends, to theradio device, control information for controlling at least one UL radiotransmission on the radio resources of the unlicensed frequencyspectrum.

According to a further embodiment of the invention, a radio device isprovided. The radio device is configured to receive, from a node of thewireless communication network, control information for semi-persistentallocation of radio resources of an unlicensed frequency spectrum.Further, the radio device is configured to, based on the controlinformation, control at least one UL radio transmission on the radioresources of the unlicensed frequency spectrum.

According to a further embodiment of the invention, a node for awireless communication network is provided. The node is configured tosemi-persistently allocate radio resources of an unlicensed frequencyspectrum to a radio device. Further, the node is configured to send, tothe radio device, control information for controlling at least one ULradio transmission on the radio resources of the unlicensed frequencyspectrum.

According to a further embodiment of the invention, a system isprovided. The system comprises a node of a wireless communicationnetwork. Further, the system comprises a radio device. The node isconfigured to send control information for semi-persistent allocation ofradio resources of an unlicensed frequency spectrum. The radio device isconfigured to receive the control information and, based on the controlinformation, control at least one UL radio transmission on the radioresources of the unlicensed frequency spectrum.

According to a further embodiment of the invention, a computer programor computer program product is provided, e.g., in the form of anon-transitory storage medium, which comprises program code to beexecuted by at least one processor of a radio device. Execution of theprogram code causes the radio device to receive, from a node of thewireless communication network, control information for semi-persistentallocation of radio resources of an unlicensed frequency spectrum.Further, execution of the program code causes the radio device to, basedon the control information, control at least one UL radio transmissionon the radio resources of the unlicensed frequency spectrum.

According to a further embodiment of the invention, a computer programor computer program product is provided, e.g., in the form of anon-transitory storage medium, which comprises program code to beexecuted by at least one processor of a node of a wireless communicationnetwork. Execution of the program code causes the node to allocate radioresources of an unlicensed frequency spectrum to a radio device.Further, the node is configured to send, to the radio device, controlinformation for controlling at least one UL radio transmission on theradio resources of the unlicensed frequency spectrum.

Details of such embodiments and further embodiments will be apparentfrom the following detailed description of embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a wireless communication system inwhich radio transmissions are controlled according to an embodiment ofthe invention.

FIG. 2 illustrates utilization of radio resources from an unlicensedspectrum according to an embodiment of the invention.

FIGS. 3A-3D illustrate allocation of radio resources according to anembodiment of the invention.

FIG. 4A schematically illustrates a collision avoidance scheme as usedaccording to an embodiment of the invention.

FIG. 4B schematically illustrates a further collision avoidance schemeas used according to an embodiment of the invention.

FIG. 5A illustrates DCI parameter settings for activation ofsemi-persistent allocation of radio resources in an unlicensed frequencyspectrum as used in an embodiment of the invention.

FIG. 5B illustrates DCI parameter settings for activation ofsemi-persistent allocation of radio resources in an unlicensed frequencyspectrum as used in an embodiment of the invention.

FIGS. 6A and 6B illustrate control elements which may be used in anembodiment of the invention.

FIG. 7 illustrates an example of processes according to an embodiment ofthe invention.

FIG. 8 shows a flowchart for schematically illustrating a methodaccording to an embodiment of the invention.

FIG. 9 shows a block diagram for illustrating functionalities of a radiodevice according to an embodiment of the invention.

FIG. 10 shows a flowchart for schematically illustrating a furthermethod according to an embodiment of the invention.

FIG. 11 shows a block diagram for illustrating functionalities of anetwork node according to an embodiment of the invention.

FIG. 12 schematically illustrates structures of a radio device accordingto an embodiment of the invention.

FIG. 13 schematically illustrates structures of a network node accordingto an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following, concepts in accordance with exemplary embodiments ofthe invention will be explained in more detail and with reference to theaccompanying drawings. The illustrated embodiments relate to control ofradio transmissions in a wireless communication network, specifically tocontrol of UL radio transmissions from a radio device, in the followingalso referred to as UE. The wireless communication network is assumed tobe based on a radio technology which may operate in an unlicensedfrequency spectrum, such as the unlicensed 3.5 GHz or 5 GHz band.Specifically, the radio technology may be based on using the LTE radiotechnology in an unlicensed frequency spectrum, e.g., using thelicensed-assisted access (LAA) technology as discussed in 3GPP TR 36.889V13.0.0 (2015-06). However, it is noted that the illustrated conceptsmay also be applied to other technologies, e.g., a 5G (5th Generation)wireless communication technology. Further, the concepts could also beapplied to standalone operation of the LTE radio technology or similarradio technology in the unlicensed frequency spectrum, withoutcoordination or other assistance by transmissions in a licensedfrequency spectrum, e.g., using MuLTEfire operation as specified inMuLTEfire Release 1.0 Technical Paper (2017-01).

In the illustrated concepts, UL radio transmissions from a UE are basedon semi-persistent allocation of radio resources. As used herein, thesemi-persistent allocation of radio resources refers to an allocation ofradio resources which is valid in a reoccurring manner in multiplesubframes, without requiring a request from the UE. However, thesemi-persistent allocation of radio resources may nonetheless becontrolled by the wireless communication network. Specifically, thewireless communication network may configure the semi-persistentallocation of radio resources, e.g., in terms of radio resources, andalso control activation and deactivation of the semi-persistentallocation of radio resources. Accordingly, by using the semi-persistentallocation of radio resources, the radio resources can be allocated tothe UE in an extended time interval starting from activation of thesemi-persistent allocation of radio resources by the wirelesscommunication network until deactivation or release of thesemi-persistent allocation of radio resources. The deactivation orrelease of the semi-persistent allocation of radio resources may beactively initiated by the wireless communication network or triggered inan implicit manner, e.g., by lack of usage of the semi-persistentlyallocated radio resources. In the following, it is assumed that thesemi-persistent allocation of radio resources in the unlicensedfrequency spectrum is based on an SPS (semi-persistent scheduling)grant, using control information conveyed on different protocol layers,in particular on a physical control channel, on a MAC (Medium AccessControl) layer, and/or on an RRC (Radio Resource Control) layer. Thesemi-persistent allocation of the radio resources may be used as analternative or in addition to dynamic allocation of radio resources inresponse to a request from the UE.

FIG. 1 schematically illustrates an exemplary scenario in which a UE 10,e.g., a mobile phone, a tablet computer, or other kind of communicationdevice, communicates with an access node 100 of the wirelesscommunication network. In accordance with the assumed utilization of theLTE radio technology, the access node 100 may also be referred to as eNB(“evolved Node B”). In the scenario of FIG. 1 , the communicationbetween the UE 10 and the access node 100 is LAA based, i.e., usescarriers from both a licensed frequency spectrum and the unlicensedfrequency spectrum. Specifically, a DL (downlink) carrier 21 from thelicensed frequency spectrum is used for DL radio transmissions from theaccess node 100 to the UE 10, and a UL carrier 22 from the licensedfrequency spectrum is used for UL radio transmissions from the UE 10 tothe access node 100. The carriers 21, 22 may also be referred to asPCell of the UE 10. In addition, a DL carrier 31 from the unlicensedfrequency spectrum may be used for DL radio transmissions from theaccess node 100 to the UE 10, and/or a UL carrier 32 from the unlicensedfrequency spectrum may be used for UL radio transmissions from the UE 10to the access node 100. It is noted that in some scenarios the samecarrier, e.g., carrier 31 or the carrier 32, could also be used for bothDL radio transmissions from the access node 100 to the UE 10 and ULradio transmissions from the UE 10 to the access node 100, e.g., byusing the carrier in a TDD (Time Division Duplex) mode. The carriers 31,32 may also be referred to as SCell of the UE 10.

FIG. 2 schematically illustrates the carriers 21, 22, 31, 32 infrequency (f) space. As illustrated, the carriers 21, 22 are in alicensed frequency spectrum, e.g., in one of the LTE bands between 700MHz and 2.7 GHz. The carriers 21, 22, which are dedicated to the LTEradio technology and licensed to the operator of the wirelesscommunication network, i.e., may not be used by other radio technologiesor operators, may be used for reliable transmission of controlinformation between the UE 10 and the access node 100. For example, oneor more DL control channels, like a PDCCH (Physical DL Control Channel)or ePDDCH (enhanced PDDCH) may be transmitted on the DL carrier 21.Similarly, one or more UL control channels, like a PUCCH (Physical ULControl Channel) may be transmitted on the UL carrier 22. Further, thecarriers may be used for transmission of a data channel. For example,one or more DL data channels, like a PDSCH (Physical DL Shared Channel)may be transmitted on the DL carrier 21. Similarly, one or more UL datachannels, like a PUSCH (Physical UL Shared Channel) may be transmittedon the UL carrier 22. The PDSCH and the PUSCH are used in a sharedmanner by multiple UEs, and allocation of radio resources of the PDSCHor PUSCH to a certain UE, like the UE 10, is accomplished by the accessnode 100. The carriers 31, 32, which are shared with other operators orradio technologies, may be used for enhancing transmission capacity ortransmission performance between the UE 10 and the access node 100.control information for the carriers 31, 32 may be transmitted on thecarriers 21, 22, i.e., transmissions on the carriers 31, 32 are assistedby transmissions on the carriers 21, 22. The carriers 31, 32 may thusalso be referred to as LAA SCell. To enhance the transmission capacityor performance, one or more DL data channels, like a PDSCH, may betransmitted on the DL carrier 31, and/or one or more UL data channels,like a PUSCH, may be transmitted on the UL carrier 32. Like in thelicensed frequency spectrum, the PDSCH and the PUSCH in the unlicensedfrequency spectrum are used in a shared manner by multiple UEs, andallocation of radio resources of the PDSCH or PUSCH to a certain UE,like the UE 10, is accomplished by the access node 100.

The operation as illustrated in FIGS. 1 and 2 , which uses separatecarriers for the DL and UL transmission direction, corresponds to an FDD(Frequency Division Duplex) mode. However, it is noted that in somescenarios DL radio transmissions and UL radio transmissions could alsobe performed on the same carrier, e.g., one of the carriers 21, 22, 31,32, using different time slots for the DL radio transmissions and ULradio transmissions, e.g., using a TDD (Time Division Duplex) mode.

In the case of standalone operation using exclusively carriers from theunlicensed frequency spectrum, e.g., MuLTEfire operation, usage of thecarriers 21, 22 could be omitted, and also control channels, like aPDCCH, ePDCCH, MF-sPUCCH or MF-ePUCCH, could be transmitted on thecarriers 31, 32 from the unlicensed frequency spectrum.

FIGS. 3A-3D illustrate the allocation of radio resources in the LTEradio technology. For the DL radio transmissions, the LTE radiotechnology uses OFDM (Orthogonal Frequency Division Multiplexing). Asillustrated in FIG. 3A, the underlying time-frequency grid is in thefrequency (f) domain defined by multiple subcarriers of 15 kHz width,and in the time (t) domain defined by a sequence of OFDM symbols forminga subframe of 1 ms duration. Each OFDM symbol starts with a cyclicprefix. A similar time-frequency grid, using the same subcarrier spacingand number of modulation symbols is used for the UL radio transmissions.For the UL radio transmissions, the LTE radio technology uses DFT(Discrete Fourier Transform) spread OFDM, also referred to assingle-carrier FDMA (Frequency Division Multiple Access). Accordingly,the radio resources of the LTE radio technology can be regarded as beingorganized in a time-frequency grid defining resource elements eachcorresponding to one subcarrier during and one modulation symbolinterval, e.g., as illustrated in FIG. 1 .

FIG. 3B further illustrates organization of the LTE radio transmissionsin the time domain. As illustrated, the radio transmissions areorganized in a sequence of radio frames, and each radio frame is formedof multiple subframes. The DL radio transmissions are organized in radioframes of 10 ms, and each of these radio frame consists of tenequally-sized subframes having a length Tsubframe=1 ms, as indicated inFIG. 3B. Each subframe comprises two slots which each have a duration of0.5 ms. Within a radio frame, the slots are sequentially numbered withina range from 0 to 19. For normal cyclic prefix length, one subframeconsists of 14 OFDM symbols, and the duration of each symbol isapproximately 71.4 μs.

The resource allocation in LTE radio technology is typically defined interms of resource blocks, where a resource block corresponds to one slot(0.5 ms) in the time domain and 12 contiguous subcarriers in thefrequency domain. A pair of two adjacent resource blocks in timedirection (1.0 ms) is also referred to as a resource block pair. Theresource blocks are indexed in the frequency domain, starting with index0 from one end of the system bandwidth.

The DL radio transmissions are typically subject to dynamic scheduling.That is to say, in each subframe the access node 100 transmits DLcontrol information (DCI). The control information indicates to whichUEs data is transmitted in this subframe, and in which resource blocksinclude the data for a specific UE. FIG. 3C shows an example of DLsubframe. As illustrated, the DCI may be transmitted in the first OFDMsymbols of the DL subframe, also referred to as control region of the DLsubframe. Typically, the control region corresponds to the first 1, 2, 3or 4 OFDM symbols of the DL subframe. The number n of the OFDM symbolsdefining the control region is also referred to as CFI (Control FormatIndicator). As illustrated, the DL subframe also contains referencesymbols, which are known to the receiver and used for demodulationpurposes, e.g., for coherent demodulation of the control information. Inthe example of FIG. 3C, CFI=3 is assumed. The reference symbols may alsoinclude cell-specific reference signals (CRSs) which may be used tosupport various functions, such as fine time and frequencysynchronization and channel estimation for certain transmission modes.

Also the UL radio transmissions are typically subject to dynamicscheduling. For this purpose, the access node 100 may indicate in theDCI information which UEs shall transmit UL data in a subsequentsubframe, and in which resource blocks the UL data is to be transmittedby the UE(s). FIG. 3D shows an example of a UL subframe. The UL resourcegrid may include UL data and UL control information. The UL data and theUL control information may be included in a shared data channel,referred to as PUSCH (Physical UL Shared Channel). Further, the ULcontrol information may be included in a control channel, referred to asPUCCH (Physical UL Control Channel). As further illustrated, a ULsubframe may also include various reference signals, such asdemodulation reference signals (DMRSs) and sounding reference signals(SRSs). DMRS are used for coherent demodulation of the PUSCH and PUCCH.The SRS are typically not associated with any data or controlinformation and are used to estimate the UL channel quality, e.g., forpurposes of frequency-selective scheduling. As illustrated in FIG. 3D,the DMRS and SRS are time-multiplexed into the UL subframe, and the SRSare transmitted in the last symbol of the UL subframe. The DMRS aretypically transmitted once every slot for subframes with normal cyclicprefix and may be located in the fourth and eleventh SC-FDMA symbols.

In the LTE radio technology, the DCI may for example indicate thefollowing information for controlling UL radio transmissions:

-   -   radio resources allocated for a UL radio transmission (including        whether frequency hopping is applied).    -   a modulation and coding scheme (MCS) to be applied for a UL        radio transmission    -   redundancy versions (RV) to be applied for a UL radio        transmission    -   a new data indicator (NDI) for controlling whether the UE shall        transmit new data or perform a retransmission    -   a transmit power control (TPC) command    -   information on DMRS to be used in a UL radio transmission    -   in the case of cross-carrier scheduling, a target carrier index        indicating a carrier to which the DCI applies.

The DCI is typically UE specific and CRC (Cyclic Redundancy Check)protected, typically using CRC bits. The UE specific character of theDCI is achieved by scrambling the CRC bits with a UE-specificidentifier, e.g., a C-RNTI (Cell Radio Network Temporary Identifier).Further, the DCI and scrambled CRC bits typically protected byconvolutional coding. Typically, the access node 100 assigns a uniqueC-RNTI to every UE associated to it. The C-RNTI can take values in therange 0001-FFF3 in hexadecimal format. When the UE 10 is simultaneouslyserved by multiple cells, such as the above-mentioned PCell and SCell,the UE 10 will typically use the same C-RNTI on all serving cells.

The DCI may be transmitted in a DL control channel referred to as PDCCH(Physical DL Control Channel), which exclusively uses resource elementsfrom the control region of the DL subframe. Further, DL controlinformation may also be transmitted in a DL control channel referred toas ePDCCH, which uses resource elements outside the control region. Aspecific type of DL control information which may be transmitted in thePDCCH or ePDCCH is scheduling information, such as a DL assignment,allocating DL radio resources for a DL radio transmission to the UE 10,or a UL grant, allocating UL radio resources for a UL radio transmissionfrom the UE 10.

The dynamic scheduling of UL radio transmissions may be accomplished inthe following manner: The UE 10 reports to the access node 100 when itneeds to transmit UL data, e.g., by sending a scheduling request (SR).In response to the SR, the access node 100 allocates the radio resourcesand sends corresponding scheduling information in an UL grant to the UE10. If the allocated radio resources are not sufficient to transmit allthe UL data, the UE 10 may further send a buffer status report (BSR) onthe allocated radio resources, thereby informing the access node 100about the amount of UL data still pending for transmission. In responseto the BSR, the access node 100 may allocate further radio resources tothe UE 10, so that the UE 10 can continue with the transmission of theUL data.

In more detail, if the UE's buffer 10 for UL data to be transmitted isempty and new UL data arrives in the buffer, dynamic scheduling may beperformed according to the following procedure:

-   -   1. Using the PUCCH, the UE 10 sends a SR to the access node 100.        The SR informs the access node 100 that the UE 10 needs to        transmit UL data. For sending the SR, the UE 10 may utilize a        timeslot which is allocated according to a periodic schedule,        e.g., with an interval of 5, 10, or 20 ms.    -   2. When the access node 100 receives the SR, it responds with a        small UL grant that allocates radio resources which are just        sufficient to indicate the amount of UL data pending in the        buffer by a BSR. This reaction to the SR typically takes 3 ms.    -   3. After the UE 10 received and processed the initial UL grant,        which may take about 3 ms, it typically sends an UL radio        transmission with the BSR. The BSR is a CE (Control Element) of        a MAC (Medium Access Control) protocol of the LTE radio        technology. If the initial UL grant is big enough, the UE 10 may        also include at least a part of the UL data into the UL radio        transmission.    -   4. Upon receiving the BSR, the access node 100 allocates radio        resources in accordance with the amount of pending UL data        indicated by the BSR and sends a corresponding further UL grant        to the UE 10. By transmitting the pending UL data on the        allocated radio resources, the UE 10 may then drain its buffer.

In the above example of a dynamic scheduling procedure, a delay of 16 msor more can occur between arrival of the UL data in the empty buffer andreception of this UL data by the access node 100. This delay can befurther increased by the UE 10 having to wait for the next opportunityto the SR and/or by the UE 10 having to perform a random accessprocedure to obtain synchronization and being allocated with SRopportunities.

A specific type of information which may be transmitted between the UE10 and the access node 100 is HARQ (Hybrid Automatic Repeat Request)feedback. For a DL radio transmission from the access node 100 to the UE10, HARQ feedback is transmitted in a UL radio transmission andindicates whether the DL radio transmission was successfully received bythe UE 10. The HARQ feedback may be transmitted the PUCCH. Successfulreception is confirmed by a positive HARQ acknowledgement (HARQ ACK).Unsuccessful reception is indicated by a negative HARQ acknowledgement(HARQ NACK). A HARQ NACK or the lack of a HARQ ACK may trigger aretransmission of the DL radio transmission. For a UL radio transmissionfrom the UE 10 to the access node 100, HARQ feedback is transmitted in aDL radio transmission and indicates whether the UL radio transmissionwas successfully received by the access node 100. The HARQ feedback maybe transmitted explicitly on a PHICH (Physical HARQ Indicator Channel)or included implicitly in DCI for future UL radio transmissions. Again,successful reception is confirmed by a HARQ ACK. Unsuccessful receptionis indicated by a HARQ NACK. A HARQ NACK or the lack of a HARQ ACK maytrigger a retransmission of the UL radio transmission. By way ofexample, 8 or 16 HARQ processes may be used in parallel.

If the LTE radio technology is used in the FDD mode, asynchronous HARQoperation may be used for the DL radio transmissions. This means thatthe HARQ processes can be used in any order. For each DL radiotransmission, the access node 100 may indicate a HARQ process ID and theRV in the PDCCH or ePDCCH, so that the UE 10 can identify to which HARQprocess a certain DL radio transmission belongs. For the UL radiotransmission, synchronous HARQ operation may be used. In this case, theUE 10 needs to use the same HARQ process number every 8 subframes. Thismeans that each subframe is associated with a corresponding HARQ processID, which allows the access node 100 to identify from the subframe indexto which HARQ process the received UL radio transmission belongs.Further, the access node 100 can know the RV from the DCI used to sendthe UL grant for this UL radio transmission. For the UL radiotransmissions either an adaptive HARQ mode or a non-adaptive HARQ modemay be used. In the adaptive HARQ mode, the UE 10 will not use thePHICH, but rather use the UL related DCI for controlling the HARQretransmissions. In the non-adaptive HARQ mode, the HARQ retransmissionsare in turn controlled on the basis of HARQ feedback indicated in thePHICH, and the UE 10 may perform the UL retransmission on the basis ofthe same parameters, e.g., resource blocks, MCS, etc., as indicated bythe DCI for the initial UL radio transmission. Using synchronous HARQoperation has the effect, that there is a fixed delay between theinitial UL radio transmission and the UL retransmission, also referredto as HARQ RTT round-trip-time. A typical HARQ RTT corresponds to 8subframes.

If the LTE radio technology is used in the FDD mode, one UL subframe maybe used to indicate HARQ feedback for multiple DL subframes, therebytaking into account that some TDD configurations have unequal numbers ofDL and UL subframes, using a PUCCH configuration which differs from thePUCCH configuration used in the FDD mode. However, it is also possibleto use the same configuration of the PUCCH as in the FDD mode, by usinga logical “AND” operation to group the HARQ feedback of multiple DLradio transmissions into a single HARQ ACK or HARQ NACK, indicatingwhether zero or more than zero blocks were received in error. In thiscase, a HARQ NACK would be transmitted if at least one of the DL radiotransmissions was unsuccessful This may have the effect that multiple DLretransmissions are triggered, even if only one of the correspondinginitial DL radio transmissions was unsuccessful.

For UL radio transmissions of the LAA SCell, asynchronous HARQ operationmay be used. That is to say, UL retransmissions may not only occur oneHARQ RTT after the initial transmission. This may facilitate consideringthat an UL retransmissions may be delayed due to LBT. For asynchronousHARQ, the UE 10 may assume that all transmitted UL radio transmissionswere successful, by locally setting the HARQ status to ACK, unless itreceives a HARQ NACK and an UL grant for a UL retransmission from theeNB.

In the case of MuLTEfire operation, transmission of HARQ feedback for aDL radio transmission may be accomplished as follows: After reception ofthe PDCCH or ePDCCH and associated PDSCH in subframe ‘n’, the UE 10 mayprepare the associated HARQ feedback for transmission in subframe ‘n+4’.The UE 10 may then transmit any pending HARQ feedback at the earliestpossible UL transmission opportunity following the ‘n+4’ constraint,i.e., in subframe n+4 or in a later subframe. The UL transmissionopportunity may be defined according to either MF-sPUCCH or MF-ePUCCHresources being available for the UE 10. When transmitting the HARQfeedback, the UE 10 may aggregate pending HARQ feedback. Accordingly,like in the above-mentioned TDD mode, the transmitted HARQ feedback maypotentially include HARQ feedback for several DL radio transmissions.The pending HARQ feedback may be aggregated in a bitmap with an implicitassociation between an index in the bitmap and a HARQ process ID. Thesize of this bitmap may be configured by the access node 100. A maximumnumber of HARQ processes for DL radio transmissions may be 16. In thebitmap, the default status of the HARQ feedback may be NACK, and thisdefault status can be changed only if there is an ACK available to besent.

Transmission of HARQ feedback for a UL radio transmission in MuLTEfireoperation may be accomplished in an asynchronous manner, similar to ULHARQ operation specified by 3GPP for eMTC (enhanced Machine TypeCommunication). Accordingly, only adaptive HARQ operation could be used,and with respect to its HARQ operation, the UE 10 may ignore anyinformation content on the PHICH, and a UL radio retransmission may betriggered and scheduled by an UL grant included in the DCI.

For usage of the carriers 31, 32 from the unlicensed frequency band, theUE 10 and the access node 100 may need to implement an LBT procedure orsimilar mechanism to avoid conflicts with other radio devices or radiotechnologies which may potentially use the carriers 31, 32. FIG. 4Aillustrates an example of an LBT procedure which may be used to ensurecoexistence with WLAN transmissions on the carrier 32.

In the example of FIG. 4A, it is assumed that two WLAN stations,referred to as station A and station B, transmit on the carrier 32 fromthe unlicensed frequency spectrum. At time t1 station A finishestransmission of a data frame to station B. After a time termed as SIFS(Short Inter Frame Space), station B sends an ACK frame back to stationA. The SIFS time may for example be 16 μs. The station B sends the ACKframe without performing a LBT operation. Before another radio device,such as the UE 10, can transmit on the carrier 32, it first needs tosense the carrier 32 to determine whether it is occupied. If, during thetransmission of the ACK frame by station B, the carrier 32 is found tobe occupied the other radio device needs to defer for a time referred toas DIFS (Distributed Inter Frame Space), which is longer than the SIFStime such as 34 μs. In this way, it can be prevented that the otherradio device interferes with the transmission of the ACK frame.Therefore, a radio device, such as the UE 10, that wishes to transmitfirst performs a CCA (Clear Channel Assessment) by sensing the carrierfor the DIFS time. If the medium is idle then the radio device assumesthat the carrier 32 is free and that it may transmit on the carrier 32.If the carrier 32 is found to be busy, the radio device waits until thecarrier 32 goes idle and defers for the DIFS time. Further, the radiodevice may wait for a random backoff period before it can start totransmit on the carrier 32 at t4. The random backoff period has thepurpose of reducing the risk of collisions when multiple radio devicesare ready to transmit when the carrier 32 goes idle. In the example ofFIG. 4A, the radio device starts a random backoff counter at t3 anddefers for a corresponding number of time slots. The random backoffcounter may be selected as a random integer of not more than a backoffcontention window size CW. To avoid recurring collisions, the backoffcontention window size CW may be doubled whenever a collision isdetected, up to a limit CWmax. When a transmission attempt is successfulwithout collision the contention window is reset back to its initialvalue.

FIG. 4B illustrates a further example of an LBT procedure which is basedon Load-based CCA according to ETSI Draft EN 301 893 V2.1.0 (2017-03).In this case, a radio device not using a WLAN protocol, such as the UE10, may use load based adaptive channel access. The radio device thatinitiates a sequence of one or more transmissions is denoted as theInitiating Device. Otherwise, the radio device is denoted as aResponding Device. The Initiating Device implements a channel accessmechanism which is based on prioritized, truncated exponential backoff.Before a transmission or a burst of transmissions on an OperatingChannel, such as the carrier 32, the Initiating Device operates at leastone Channel Access Engine (up to four access engines can be operatedsimultaneously, corresponding to different data priority classes) thatexecutes a procedure described in step 1) to step 8) below. A singleObservation Slot shall have a duration of not less than 9 μs.

-   1) The Channel Access Engine sets a contention window CW to a    minimum value CWmin.-   2) The Channel Access Engine selects a random number q from a    uniform distribution over the range 0 to CW.-   3) The Channel Access Engine initiates a Prioritization Period as    described in step 3) a) to step 3) c):    -   a) The Channel Access Engine sets p according to the priority        class associated with this Channel Access Engine    -   b) The Channel Access Engine waits for a period of 16 μs.    -   c) The Channel Access Engine performs CCA on the Operating        Channel during a single Observation Slot:        -   i) The Operating Channel is considered occupied if other            transmissions within this channel are detected with a level            above an ED (Energy Detect) threshold. In this case, the            Channel Access Engine shall initiate a new Prioritization            Period starting with step 3) a) after the energy within the            channel has dropped below the ED threshold.        -   ii) In case no energy within the Operating Channel is            detected with a level above the ED threshold, p may be            decremented by not more than 1. If p is equal to 0, the            Channel Access Engine shall proceed with step 4), otherwise            the Channel Access Engine shall proceed with step 3) c).-   4) The Channel Access Engine performs a Backoff Procedure as    described in step 4) a) to step 4)d):    -   a) This step verifies if the Channel Access Engine satisfies the        Post Backoff condition. If q<0 and the Channel Access Engine is        ready for a transmission, the Channel Access Engine shall set CW        equal to CWmin and shall select a random number q from a uniform        distribution over the range 0 to CW before proceeding with        step 4) b).    -   b) If q<1 the Channel Access Engine proceeds with step 4) d).        Otherwise, the Channel Access Engine may decrement the value q        by not more than 1 and the Channel Access Engine shall proceed        with step 4) c).    -   c) The Channel Access Engine shall perform CCA on the Operating        Channel during a single Observation Slot    -   d) If the Channel Access Engine is ready for a transmission the        Channel Access Engine shall continue with step 5). Otherwise,        the Channel Access Engine shall decrement the value q by 1 and        the Channel Access Engine shall proceed with step 4) c). It        should be understood that q can become negative and keep        decrementing as long as the Channel Access Engine is not ready        for a transmission.-   5) If only one Channel Access Engine of the Initiating Device is in    this stage the Channel Access Engine proceeds with step 6). If the    Initiating Device has a multitude of Channel Access Engines in this    stage, the Channel Access Engine with highest Priority Class in this    multitude shall proceed with step 6) and all other Channel Access    Engines in the current stage shall proceed with step 8).-   6) The Channel Access Engine may start transmissions belonging to    the corresponding or higher Priority Classes, on one or more    Operating Channels.    -   a) The Channel Access Engine can have multiple transmissions        without performing an additional CCA on this Operating Channel        providing the gap in between such transmissions does not exceed        16μ s. Otherwise, if this gap exceeds 16μ s and does not exceed        25μ s, the Initiating Device may continue transmissions provided        that no energy was detected with a level above the ED threshold        for a duration of one Observation Slot.    -   b) The Channel Access Engine may grant an authorization to        transmit on the current Operating Channel to one or more        Responding Devices. If the Initiating Device issues such a        transmission grant to a Responding Device, the Responding Device        shall operate according to the procedure described below after        Step 8.    -   c) The Initiating Device may have simultaneous transmissions of        Priority Classes lower than the Priority Class of the Channel        Access Engine, provided that the corresponding transmission        duration (Channel Occupancy Time) is not extended beyond the        time that is needed for the transmission(s) corresponding to the        Priority Class of the Channel Access Engine.-   7) When the Channel Occupancy has completed, and it has been    confirmed that at least one transmission that started at the    beginning of the Channel Occupancy was successful, the Initiating    Device proceeds with step 1) otherwise the Initiating Device    proceeds with step 8).-   8) The Initiating Device may retransmit. If the Initiating Device    does not retransmit the Channel Access Engine shall discard all data    packets associated with the unsuccessful Channel Occupancy and the    Channel Access Engine shall proceed with step 1). Otherwise, the    Channel Access Engine shall adjust CW to ((CW+1)×m)−1 with m≥2. If    the adjusted value of CW is greater than CWmax the Channel Access    Engine may set CW equal to CWmax. The Channel Access Engine shall    then proceed with step 2).

The Responding Device may transmit either without performing a CCA, ifthese transmissions are initiated at most 16μ s after the lasttransmission by the Initiating Device that issued the grant, or itperforms CCA on the Operating Channel during a single observation slotwithin a 25 μs period ending immediately before the granted transmissiontime.

For an LTE based UL radio transmissions using dynamic scheduling, therequirement for an LBT procedure or similar CCA based mechanism may havethe effect that the UE 10 needs to perform an LBT procedure before itcan send a SR, that the access node 100 needs to perform an LBTprocedure before it can send an UL grant, and that the UE 10 needs toperform an LBT procedure before it can perform the UL radiotransmission. As compared to other radio technologies which do not usedynamic scheduling, such as WLAN, this may reduce the chances of the UE10 of gaining access to the carrier 32. Accordingly, the concepts asdescribed herein involve using semi-persistent allocation of radioresources for the UL radio transmissions in the unlicensed frequencyspectrum. Using the semi-persistent allocation of radio resources, theUE 10 can start the UL radio transmission without obtaining permissionfrom the access node 100. In other words, as long as the semi-persistentallocation is valid, the UE 10 can immediately perform the LBT procedureto gain access to UL carrier 32, without having to transmit a SR orhaving to wait until it receives an UL grant from the access node 100.

In the examples as further detailed below, SPS may be used in theunlicensed spectrum, e.g., by enabling SPS for an LAA SCell or forMuLTEfire operation. RRC may be used to configure SPS for UL radiotransmissions in one or more SCells in the unlicensed frequency spectrum(e.g., for LAA or MuLTEfire). Further, RRC may be used to configure SPSfor UL radio transmissions in one or more PCells in the unlicensedfrequency spectrum (e.g., for MuLTEfire). A corresponding SPS grant willin the following also be referred to as US-SPS grant (unlicensedspectrum SPS grant). Activation and/or release of the US-SPS grant maybe signalled from the access node 100 to the UE 10 on a physical controlchannel, such as the PDCCH or ePDCCH, thereby ensuring fast activationor deactivation. As further explained below, this may be achieved byusing DCI format 0A/4A with some fields set to special values. Further,a MAC CE may be used for confirming activation or deactivation of theSPS grant. This MAC CE may indicate for each of multiple carriers, e.g.,multiple SCells or PCell and SCell, whether the US-SPS grant is activeor in active, e.g., in terms of a bitmap. The MAC CE could also indicatewhether an SPS grant for a carrier from the licensed spectrum is activeor inactive.

To accomplish RRC based configuration of SPS in the unlicensed frequencyband, an RRC message may be transmitted which includes an InformationElement (IE) defining a configuration to be applied for SPS in theunlicensed frequency band. This may be achieved by modifying orsupplementing the SPS-config IE as defined in section 6.3.2 of 3GPP TS36.331 V14.1.0 (2016-12). The IE may define multiple configurations,each pertaining to a corresponding carrier from the unlicensed frequencyband, e.g., to an SCell or PCell. The RRC IE may also define multipleconfigurations, of which at least one pertains to a correspondingcarrier from the unlicensed frequency band, e.g., to an SCell and atleast one pertains to a corresponding carrier from the licensedfrequency band, e.g. to a PCell or SCell. Accordingly, the IE mayindicate separate SPS configurations for one or more carriers,corresponding either to an SCell or to a PCell, and at least one ofthese carriers may be from the unlicensed frequency spectrum.

In addition or as an alternative, the RRC IE may indicate a set of oneor more maximum UL burst lengths that must be observed by the UE 10 whenusing the radio resources allocated by the UL-SPS grant. The maximum ULburst length may be used to optimize the coexistence with other radiotechnologies.

In addition or as an alternative, the RRC IE may include an indicationof a set of DL serving cells for which HARQ feedback and/or CSI (ChannelState Information) is to be reported by using UL radio transmissions onthe resources allocated by the US-SPS grant. The access node 100 canseparately configure the set of DL serving cells for which to reportHARQ ACK and/or CSI, e.g., to report the HARQ feedback and/or CSIaccording to one of the following options: using a grant-less PUSCH withUL-SCH, i.e., a data channel which is defined on the US-SPS radioresources and which also supports transmission of user-plane data,grant-less PUSCH without UL-SCH, i.e., a data channel which is definedon the US-SPS radio resources and which does not support additionaltransmission of user-plane data, and/or grant-less PUCCH or ePUCCH,i.e., a physical UL control channel.

In addition or as an alternative, the RRC IE may indicate one or moreseparate configurations to be applied for bundling of HARQ feedback inthe spatial domain, time domain, and/or frequency domain, when ULcontrol information is transmitted on a data channel defined on theUS-SPS radio resources.

In addition or as an alternative, the RRC IE may indicate aconfiguration of time-domain, code-domain, and/or frequency-domainresource parameters for multiplexing of transmissions on an UL controlchannel defined on the US-SPS radio resources.

In addition or as an alternative, the RRC IE may indicate a UE specificLBT backoff offset: To avoid intra-cell collisions due to an alignedstarting point of transmissions by different UEs sharing at least a partof the US-SPS radio resources, a UE-specific offset may be added toregular backoff required by the LBT procedure, e.g., as explained inconnection with FIG. 4A or 4B, and this offset may be indicated by theRRC IE.

The US-SPS grant may be activated or released by sending controlinformation on a physical control channel, e.g., a PDCCH or ePDCCH. Thecontrol channel may be transmitted on a PDCCH or ePDCCH of the cell(SCell or PCell) for which the US-SPS allocates the radio resources.However, it is also possible to utilize cross carrier scheduling and thesend the control information on a physical control channel of anothercell. For sending the control information on the physical controlchannel, the access node 100 may utilize DCI format 0, DCI format 0A, orDCI format 4A, as for example defined in 3GPP TS 36.212 V14.1.1(2017-01), with some parameters or fields set to special values. If theUS-SPS grant is activated or deactivated by cross carrier scheduling,the DCI may include an indication of the target carrier or cell, e.g.,in the carrier index field (CIF) as defined for DCI format 0A and 4A.Otherwise, the CIF does not need to be included.

To take into account that the access node 100 can activate, release orre-activate the US-SPS at any time, the UE 10 should continuouslymonitor the PDCCH or ePDCCH for the control information which controlsactivation and release of the US-SPS grant. This may be accomplishedusing DCI format 0A or 4A on the PDCCH or ePDCCH of the PCell if crosscarrier scheduling is used or using DCI format 0A or 4A on the PDCCH orePDCCH of the SCell if cross carrier scheduling is not used.

The UE 10 may activate the US-SPS grant if the following conditions aremet for the control information received on the physical controlchannel:

-   -   The CRC bits of the DCI are scrambled with either a UE specific        SPS-C-RNTI, i.e., a C-RNTI specifically assigned for the purpose        of SPS control, or a group SPS-RNTI which is assigned to        multiple UEs and can be used for group based SPS activation for        these UEs.    -   The NDI field is set to ‘0’.    -   The fields of the DCI are set according to the table of FIG. 5A.

In the DCI as illustrated in FIG. 5A, the access node 100, i.e., theeNB, may control the following fields:

-   -   Cyclic shift DM RS: The eNB may assign each UE with different        DMRS cyclic shift.    -   Value of CSI request: The eNB can either set the field: to A) a        fixed value, to B) “activate CSI based on higher layer        configuration”, or to C) “applies to first UL burst”. In the        case of option A), the DCI will either request the UE 10 to send        DCI or not. In the case of option B) the sending of CSI by the        UE 10 will be controlled by higher layer configuration, e.g., by        RRC configuration. In the case of option C), the DCI requests        the UE 10 to send the CSI only in the first UL burst on the        US-SPS resources.    -   Value of SRS request: The eNB can either set the field: to A) a        fixed value, to B) “activate SRS based on higher layer        configuration”, or to C) “applies to first UL burst”. In the        case of option A), the DCI will either request the UE 10 to send        SRS or not. In the case of option B) the sending of SRS by the        UE 10 will be controlled by higher layer configuration, e.g., by        RRC configuration. In the case of option C), the DCI requests        the UE 10 to send the SRS only in the first UL burst on the        US-SPS resources.    -   Value of PUSCH start point: The eNB may set the field to A) a        fixed value to defining the PUSCH start point or to B) a value        which defines the PUSCH start point only for the first UL burst        on the US-SPS resources.    -   Value of PUSCH end point: The eNB may set the field to A) a        fixed value to defining the PUSCH end point or to B) a value        which defines the PUSCH end point only for the first UL burst on        the US-SPS resources.    -   Resource block assignment: Using this field the eNB may assign        interlaces for the US-SPS grant according to resource allocation        type 3.    -   Modulation and coding scheme: Using this field, the eNB may        define the MCS to be used on the US-SPS resources. The MSB of        this field is not fixed to zero. Accordingly the eNB can choose        any possible MCS with RV zero, also an MCS with order of more        than 4.    -   CIF: The eNB may use this field to indicate the carrier to which        the US-SPS grant activation applies.

In addition, the eNB can trigger sending of UL control information foron the PUSCH without a data channel for user data, e.g., by setting oneor more fields in the DCI to special values. For example, the eNB canachieve this by setting the channel access type and priority class fieldto 1s or by setting the PUSCH trigger A field to 1s.

The UE 10 may release the US-SPS grant if the following conditions aremet for the control information received on the physical controlchannel:

-   -   The CRC bits of the DCI are scrambled with either a UE specific        SPS-C-RNTI, i.e., a C-RNTI specifically assigned for the purpose        of SPS control, or a group SPS-RNTI which is assigned to        multiple UEs and can be used for group based SPS deactivation        for these UEs.    -   The NDI field is set to ‘0’.    -   The fields of the DCI are set according to the table of FIG. 5B.

For confirming activation or deactivation of the US-SPS grant, the UE 10may send a MAC message to the access node 100. Specifically, the SPSconfirmation MAC CE as defined in section 6.3.1.11 of 3GPP TS 36.321V14.1.0 (2016-12) may be modified or supplemented for this purpose, or anew MAC CE can be defined for this purpose. If the SPS confirmation MACCE is used, it may be identified by LCID (logical channel identifier)“10101” in a header of the MAC message. If MAC CE dedicated for thepurpose of US-SPS grant confirmation is used, it may be identifier byanother LCID assigned to MAC CEs of this type.

The MAC CE for confirming activation or deactivation of the US-SPS granthas a fixed size and consists of at least one multi-bit value. For thecase that no serving cell has a ServCellIndex (serving cell index)larger than 8, the MAC CE can consist of a single octet defining eightfields. Otherwise the MAC CE may consist of four octets, each definingeight fields. Each field is mapped to a corresponding cell, e.g., PCellor SCell, and consists of one bit which indicates whether the US-SPSgrant is activated. For example, a bit value of “1” may indicate thatthe US-SPS grant is activated for the corresponding cell, while a bitvalue of “0” indicates that the US-SPS grant is deactivated for thecorresponding cell. FIG. 6A shows an example of the MAC CE for the caseof using only one octet O1. FIG. 6B shows an example of the MAC CE forthe case of using four octets O1, O2, O3, O4.

As illustrated, each octet includes eight values denoted by Ci, where iis a cell index, e.g., corresponding to the SCellIndex of an SCell. Thevalue of Ci indicates whether for the corresponding SCell the US-SPSgrant is activated or deactivated, i.e., an SPS activation/deactivationstatus. By way of example, Ci may be set to “1” to indicate that theUS-SPS grant is activated for cell index i, while Ci is set to “0” toindicate that the US-SPS grant is deactivated for cell index i. If nocell with cell index i is configured, the corresponding Ci field may beignored.

According to 3GPP TS 36.321 V14.1.0, LCID 10101 identifies a MAC CE witha fixed size of zero bits. In order to support this legacy behavior, theUE 10 and the access node 100 may be configured to distinguish betweenthe case that the LCID 10101 identifies the legacy SPS confirmation MACCE with zero length and the case that the LCID identifies theabove-mentioned MAC CE consisting of at least one multi-bit value. Forexample, the UE 10 and the access node 100 could use a higher layerconfiguration procedure, e.g., RRC configuration, to select between thetwo cases. In this way, the UE 10 can be controlled whether to send thelegacy SPS confirmation MAC CE with zero length or the above-mentionedMAC CE consisting of at least one multi-bit value. Similarly, the accessnode 100 can be made aware whether to expect the legacy SPS confirmationMAC CE with zero length or the above-mentioned MAC CE consisting of atleast one multi-bit value.

The MAC CE for confirming activation or deactivation of the US-SPS grantmay be sent on the US-SPS grant resources, e.g., on a logical datachannel defined on these radio resources, such as a UL-SCH. However, theMAC for confirming activation or deactivation of the US-SPS grant couldalso be sent on other radio resources which are available for UL radiotransmissions, e.g., dynamically scheduled radio resources. Further, itis noted that the MAC CE could also be used for confirming activation ordeactivation of an SPS grant on any type of cell or carrier, includingthe PCell or one or more SCells in the licensed spectrum. In somescenarios, the MAC CE could be sent on the same carrier to which theUS-SPS grant pertains, thereby implicitly indicating to which carrier orcell the confirmation of activation/deactivation relates. In this case,also the legacy SPS confirmation MAC CE can be used for indicating theconfirmation of activation/deactivation.

It is noted that a similar MAC CE as explained above could also be usedin the DL direction to control activation or release of the US-SPSgrant.

FIG. 7 shows exemplary processes which are based on the above-describedconcepts. The processes of FIG. 7 involve the UE 10 and the access node(AN) 100. The UE 10 and the access node 100 are assumed to use LAA basedcommunication or MuLTEfire based communication on one or more carriersfrom an unlicensed spectrum, such as the above-mentioned carrier 32.

In the processes of FIG. 7 , the access node 100 sends an RRC message701 to the UE 10. The RRC message includes SPS configurationinformation. For example, the SPS configuration information may indicateradio resources allocated by SPS on the carrier(s) from the unlicensedspectrum. The SPS configuration information may define separateconfigurations multiple carriers, e.g., corresponding either to an SCellor to a PCell, and at least one of these carriers may be from theunlicensed frequency spectrum. Further, the SPS configurationinformation may indicate a set of one or more maximum UL burst lengthsthat must be observed by the UE 10 when using the radio resourcesallocated by the UL-SPS grant. Further, the SPS configurationinformation may include an indication of a set of DL serving cells forwhich HARQ feedback and/or CSI (Channel State Information) is to bereported by using UL radio transmissions on the resources allocated bySPS on the carrier(s) from the unlicensed spectrum. Further, the SPSconfiguration information may indicate one or more separateconfigurations to be applied for bundling of HARQ feedback in thespatial domain, time domain, and/or frequency domain, when UL controlinformation is transmitted on a data channel defined on the radioresources allocated by SPS on the carrier(s) from the unlicensedspectrum. Further, the SPS configuration information may indicate aconfiguration of time-domain, code-domain, and/or frequency-domainresource parameters for multiplexing of transmissions on an UL controlchannel defined on the radio resources allocated by SPS on thecarrier(s) from the unlicensed spectrum. Further, the SPS configurationinformation may indicate a UE specific LBT backoff offset.

To activate the US-SPS grant, the access node 100 then sends DCI 702 onthe PDCCH or ePDCCH. This may be accomplished as explained above, usingDCI format 0A or DCI format 4A. The UE 10 then confirms activation ofthe US-SPS grant by sending a MAC message 703 to the access node 100.The MAC message 703 may include the above-mentioned MAC CE forconfirming activation/deactivation of the US-SPS grant. The MAC CE mayinclude at least one multi-bit value to confirm the activation statusfor multiple carriers.

With the US-SPS grant being activated, the UE 10 can perform UL radiotransmissions on the radio resources allocated by SPS on the carrier(s)from the unlicensed spectrum, i.e., the US-SPS resources. As indicatedby block 704, this involves that the UE 10 first performs CCA, and thensends an UL radio transmission 705 on the US-SPS resources. The accessnode 100 responds with HARQ feedback 706 to the UL radio transmission605.

Since the US-SPS grant is valid in for radio resources which reoccurperiodically, the UE 10 may perform multiple UL radio transmissions onthe US-SPS resources, without requiring further scheduling by the accessnode 100. In the example of FIG. 7 , the UE 10 again performs CCA atblock 707 and then a further UL radio transmission 708 on the US-SPSresources, and the access node 100 then sends HARQ feedback 709 for theUL radio transmission 708. Further, the UE 10 again performs CCA atblock 710 and then a still further UL radio transmission 711 on theUS-SPS resources, and the access node 100 then sends HARQ feedback 712for the UL radio transmission 711.

In the example of FIG. 7 , the access node 100 then decides to releasethe US-SPS grant for the UE 10. Accordingly, the access node 100 sendsDCI 713 on the PDCCH or ePDCCH to the UE 10. The DCI 713 indicatesrelease of the US-SPS grant. The access node 100 may send the DCI 713 asexplained above, using DCI format 0, DCI format 0A, or DCI format 4A.The UE 10 then confirms deactivation of the US-SPS grant by sending aMAC message 714 to the access node 100. The MAC message 714 may includethe above-mentioned MAC CE for confirming activation/deactivation of theUS-SPS grant. The MAC CE may include at least one multi-bit value toconfirm the activation status for multiple carriers.

FIG. 8 shows a flowchart for illustrating a method of controlling radiotransmissions. The method of FIG. 8 may be utilized for implementing theillustrated concepts in a radio device, such as the above-mentioned UE10. If a processor-based implementation of the radio device is used, thesteps of the method may be performed by one or more processors of theradio device. In such a case the radio device may further comprise amemory in which program code for implementing the below describedfunctionalities is stored.

At step 810, the radio device receives control information from a nodeof the wireless communication network. The node may correspond to anaccess node of the wireless communication network, such as theabove-mentioned access node 100. The control information has the purposeof controlling semi-persistent allocation of radio resources of anunlicensed frequency spectrum. For example, the control information maybe used for controlling the above-mentioned US-SPS grant. The radiodevice may receive the control information on a physical layer protocollevel, e.g., on a physical control channel, such as a PDCCH or ePDCCH.Further, the radio device may receive the control information on a MAClayer protocol level, e.g., in a MAC CE. Further, the radio device mayreceive the control information on a higher layer protocol level, e.g.,in one or more RRC messages.

The control information may define a first configuration applicable fora first UL carrier and a second configuration applicable for a second ULcarrier. Accordingly, for each of multiple UL carriers, the controlinformation may define a corresponding configuration for controlling thesemi-persistent allocation of radio resources. At least one of thesemultiple UL carriers may be from the unlicensed frequency spectrum. Theconfigurations may be defined by one or more messages of an RRCprotocol.

Further, the control information, e.g., as received in one or moremessages of an RRC protocol, may indicate at least one maximum burstlength allowed for the at least one UL radio transmission on the radioresources of the unlicensed frequency spectrum.

Further, the control information, e.g., as received in one or moremessages of an RRC protocol, may indicate at least one DL carrier. Theat least one UL radio transmission may then include UL controlinformation for the at least one DL carrier. One or more messages of anRRC protocol may thus be used to define a configuration of using theradio resources from the unlicensed frequency spectrum for transmissionof UL control information related to a certain DL carrier. The ULcontrol information may include HARQ feedback for one or more DL radiotransmissions on the at least one DL carrier. Alternatively or inaddition, wherein the UL control information may include CSI for the atleast one DL carrier.

Further, the control information may indicate, e.g., as received in oneor more messages of an RRC protocol, a configuration applicable fortransmission of UL control information by the at least one UL radiotransmission on the radio resources of the unlicensed frequencyspectrum. For example, the control information could indicate aconfiguration applicable for bundling the UL control information in thetime domain, spatial domain, and/or frequency domain. Further, thecontrol information could indicate a configuration applicable formultiplexing different UL radio transmissions on the radio resources ofthe unlicensed frequency spectrum.

Further, the control information, e.g., as received in one or moremessages of an RRC protocol, may indicate, a configuration applicablefor multiplexing different UL control channel transmissions on the radioresources of the unlicensed frequency spectrum.

Further, the control information, e.g., as received in one or moremessages of an RRC protocol, may indicate one or more parameters of anLBT procedure to be applied by the radio device for controlling the atleast one UL radio transmission on the radio resources of the unlicensedfrequency spectrum. Examples of such LBT procedure are explained inconnection with FIGS. 4A and 4B. For example, the one or more parametersof the LBT procedure may include a backoff offset. The backoff offsetmay control a delay applied before starting a transmission when theradio resources were detected to be unoccupied. The backoff offset maydiffer from a backoff offset applied by one or more other radio devicesusing the radio resources of the unlicensed frequency spectrum. That isto say, the backoff offset may be set in a device-specific manner.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate activation ofthe semi-persistent allocation of radio resources of the unlicensedfrequency spectrum.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate a cyclic shiftof a demodulation reference signal to be transmitted by the radio deviceon the radio resources of the unlicensed frequency spectrum. The cyclicshift of the demodulation reference signal may differ from a cyclicshift applied by one or more other radio devices for transmission of ademodulation reference signal on the radio resources of the unlicensedfrequency spectrum. That is to say, the cyclic shift may be devicespecific.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may request the radio deviceto transmit one or more SRS on the radio resources of the unlicensedfrequency spectrum.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may requests the radiodevice to transmit one or more SRS in a first burst of the at least oneUL radio transmission on the radio resources of the unlicensed frequencyspectrum.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may request the radio deviceto transmit CSI on the radio resources of the unlicensed frequencyspectrum.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may request the radio deviceto transmit CSI in a first burst of the at least one UL radiotransmission on the radio resources of the unlicensed frequencyspectrum.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate a start symbolof an UL data channel on the radio resources of the unlicensed frequencyspectrum, e.g., a start symbol of a PUSCH.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate the startsymbol of an UL data channel in a first burst of the at least one ULradio transmission on the radio resources of the unlicensed frequencyspectrum, e.g., a start symbol of a PUSCH.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate an end symbolof an UL data channel on the radio resources of the unlicensed frequencyspectrum, e.g., an end symbol of a PUSCH.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicates an end symbolof an UL data channel in a first burst of the at least one UL radiotransmission on the radio resources of the unlicensed frequencyspectrum, e.g., an end symbol of a PUSCH.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate an MCS to beapplied for the at least one UL radio transmission on the radioresources of the unlicensed frequency spectrum. The modulation andcoding scheme may have a modulation order of more than 4.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicates at least oneUL carrier which provides the radio resources of the unlicensedfrequency spectrum, e.g., in the above-mentioned CIF.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may request the radio deviceto send UL control information on an UL data channel on the radioresources of the unlicensed frequency spectrum, e.g., on a PUSCH. The ULdata channel may be configured with a logical data channel for higherlayer data. For example, the data channel could be a PUSCH and beconfigured with a UL-SCH or without a UL-SCH.

Further, the control information, e.g., as received on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate release of thesemi-persistent allocation of radio resources of the unlicensedfrequency spectrum.

At step 820, the radio device controls at least one UL radiotransmission on the radio resources of the unlicensed frequencyspectrum. This is accomplished based on the control information receivedat step 810.

At step 830, the radio device sends confirmation information to the nodeof the wireless communication network. The confirmation informationindicates whether the semi-persistent allocation of radio resources isactivated. If the semi-persistent allocation is used on multiple ULcarriers, the confirmation information may indicate individually foreach of the multiple UL carriers whether the semi-persistent allocationof radio resources is activated. The radio device may transmit theconfirmation information in a control element of a MAC protocol, such asthe above-described MAC CE for confirming activation/deactivation of theUS-SPS grant. To convey the confirmation for the multiple UL carriers,the MAC CE may consist of one or more multibit values. In such multibitvalue, each bit may indicate the activation status of a corresponding ULcarrier.

FIG. 9 shows a block diagram for illustrating functionalities of a radiodevice 900 which operates according to the method of FIG. 8 . Asillustrated, the radio device 900 may be provided with a module 910configured to receive control information, such as explained inconnection with step 810. Further, the radio device 900 may be providedwith a module 920 configured to control at least one UL radiotransmission on radio resources from an unlicensed frequency, such asexplained in connection with step 820. Further, radio device 900 may beprovided with a module 930 configured to send confirmation information,such as explained in connection with step 830.

It is noted that the radio device 900 may include further modules forimplementing other functionalities, such as known functionalities of aUE supporting the LTE radio technology. Further, it is noted that themodules of the radio device 900 do not necessarily represent a hardwarestructure of the radio device 900, but may also correspond to functionalelements, e.g., implemented by hardware, software, or a combinationthereof.

FIG. 10 shows a flowchart for illustrating a method of controlling radiotransmissions. The method of FIG. 10 may be utilized for implementingthe illustrated concepts in a node of a wireless communication network,such as the above-mentioned access node 100. If a processor-basedimplementation of the node is used, the steps of the method may beperformed by one or more processors of the radio device. In such a casethe node may further comprise a memory in which program code forimplementing the below described functionalities is stored.

At step 1010, the node semi-persistently allocates radio resources of anunlicensed frequency spectrum to a radio device. The radio device mayfor example correspond to a UE, such as the above-mentioned UE 10.

At step 1030, the node sends control information to the radio device.The control information has the purpose of controlling at least one ULradio transmission on the radio resources of the unlicensed frequencyspectrum. For example, the control information may be used forcontrolling the above-mentioned US-SPS grant. The node may send thecontrol information on a physical layer protocol level, e.g., on aphysical control channel, such as a PDCCH or ePDCCH. Further, the radiodevice may receive the control information on a MAC layer protocollevel, e.g., in a MAC CE. Further, the radio device may receive thecontrol information on a higher layer protocol level, e.g., in one ormore RRC messages.

The control information may define a first configuration applicable fora first UL carrier and a second configuration applicable for a second ULcarrier. Accordingly, for each of multiple UL carriers, the controlinformation may define a corresponding configuration for controlling thesemi-persistent allocation of radio resources. At least one of thesemultiple UL carriers may be from the unlicensed frequency spectrum. Theconfigurations may be defined by one or more messages of an RRCprotocol.

Further, the control information, e.g., as transmitted in one or moremessages of an RRC protocol, may indicate at least one maximum burstlength allowed for the at least one UL radio transmission on the radioresources of the unlicensed frequency spectrum.

Further, the control information, e.g., as transmitted in one or moremessages of an RRC protocol, may indicate at least one DL carrier. Theat least one UL radio transmission may then include UL controlinformation for the at least one DL carrier. One or more messages of anRRC protocol may thus be used to define a configuration of using theradio resources from the unlicensed frequency spectrum for transmissionof UL control information related to a certain DL carrier. The ULcontrol information may include HARQ feedback for one or more DL radiotransmissions on the at least one DL carrier. Alternatively or inaddition, wherein the UL control information may include CSI for the atleast one DL carrier.

Further, the control information may indicate, e.g., as transmitted inone or more messages of an RRC protocol, a configuration applicable fortransmission of UL control information by the at least one UL radiotransmission on the radio resources of the unlicensed frequencyspectrum. For example, the control information could indicate aconfiguration applicable for bundling the UL control information in thetime domain, spatial domain, and/or frequency domain. Further, thecontrol information could indicate a configuration applicable formultiplexing different UL radio transmissions on the radio resources ofthe unlicensed frequency spectrum.

Further, the control information, e.g., as transmitted in one or moremessages of an RRC protocol, may indicate, a configuration applicablefor multiplexing different UL control channel transmissions on the radioresources of the unlicensed frequency spectrum.

Further, the control information, e.g., as transmitted in one or moremessages of an RRC protocol, may indicate one or more parameters of anLBT procedure to be applied by the radio device for controlling the atleast one UL radio transmission on the radio resources of the unlicensedfrequency spectrum. Examples of such LBT procedure are explained inconnection with FIGS. 4A and 4B. For example, the one or more parametersof the LBT procedure may include a backoff offset. The backoff offsetmay control a delay applied before starting a transmission when theradio resources were detected to be unoccupied. The backoff offset maydiffer from a backoff offset applied by one or more other radio devicesusing the radio resources of the unlicensed frequency spectrum. That isto say, the backoff offset may be set in a device-specific manner.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate activation ofthe semi-persistent allocation of radio resources of the unlicensedfrequency spectrum.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate a cyclic shiftof a demodulation reference signal to be transmitted by the radio deviceon the radio resources of the unlicensed frequency spectrum. The cyclicshift of the demodulation reference signal may differ from a cyclicshift applied by one or more other radio devices for transmission of ademodulation reference signal on the radio resources of the unlicensedfrequency spectrum. That is to say, the cyclic shift may be devicespecific.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may request the radio deviceto transmit one or more SRS on the radio resources of the unlicensedfrequency spectrum.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may requests the radiodevice to transmit one or more SRS in a first burst of the at least oneUL radio transmission on the radio resources of the unlicensed frequencyspectrum.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may request the radio deviceto transmit CSI on the radio resources of the unlicensed frequencyspectrum.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may request the radio deviceto transmit CSI in a first burst of the at least one UL radiotransmission on the radio resources of the unlicensed frequencyspectrum.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate a start symbolof an UL data channel on the radio resources of the unlicensed frequencyspectrum, e.g., a start symbol of a PUSCH.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate the startsymbol of an UL data channel in a first burst of the at least one ULradio transmission on the radio resources of the unlicensed frequencyspectrum, e.g., a start symbol of a PUSCH.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate an end symbolof an UL data channel on the radio resources of the unlicensed frequencyspectrum, e.g., an end symbol of a PUSCH.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicates an end symbolof an UL data channel in a first burst of the at least one UL radiotransmission on the radio resources of the unlicensed frequencyspectrum, e.g., an end symbol of a PUSCH.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate an MCS to beapplied for the at least one UL radio transmission on the radioresources of the unlicensed frequency spectrum. The modulation andcoding scheme may have a modulation order of more than 4.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicates at least oneUL carrier which provides the radio resources of the unlicensedfrequency spectrum, e.g., in the above-mentioned CIF.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may request the radio deviceto send UL control information on an UL data channel on the radioresources of the unlicensed frequency spectrum, e.g., on a PUSCH. The ULdata channel may be configured with a logical data channel for higherlayer data. For example, the data channel could be a PUSCH and beconfigured with a UL-SCH or without a UL-SCH.

Further, the control information, e.g., as transmitted on a physicalcontrol channel, such as a PDCCH or ePDCCH, may indicate release of thesemi-persistent allocation of radio resources of the unlicensedfrequency spectrum.

At step 1030, the node receives confirmation information to the node ofthe wireless communication network. The confirmation informationindicates whether the semi-persistent allocation of radio resources isactivated. If the semi-persistent allocation is used on multiple ULcarriers, the confirmation information may indicate individually foreach of the multiple UL carriers whether the semi-persistent allocationof radio resources is activated. The node may receive the confirmationinformation in a control element of a MAC protocol, such as theabove-described MAC CE for confirming activation/deactivation of theUS-SPS grant. To convey the confirmation for the multiple UL carriers,the MAC CE may consist of one or more multibit values. In such multibitvalue, each bit may indicate the activation status of a corresponding ULcarrier.

FIG. 11 shows a block diagram for illustrating functionalities of a node1100 which operates according to the method of FIG. 10 . As illustrated,the node 1100 may be provided with a module 1110 configured tosemi-persistently allocate radio resources from an unlicensed frequencyspectrum, such as explained in connection with step 1010. Further, thenode 1100 may be provided with a module 1120 configured to send controlinformation for controlling at least one UL radio transmission on radioresources from the unlicensed frequency, such as explained in connectionwith step 1020. Further, node 1100 may be provided with a module 1130configured to receive confirmation information, such as explained inconnection with step 1030.

It is noted that the node 1100 may include further modules forimplementing other functionalities, such as known functionalities of aeNB of the LTE radio technology or other kind of access node. Further,it is noted that the modules of the node 1100 do not necessarilyrepresent a hardware structure of the node 1100, but may also correspondto functional elements, e.g., implemented by hardware, software, or acombination thereof.

It is to be understood that the methods of FIGS. 8 and 10 may also becombined, e.g., in a system including a radio device operating accordingto the method of FIG. 8 and a node operating according to the method ofFIG. 10 . In such system, the node could send the control informationfor semi-persistent allocation of radio resources of an unlicensedfrequency spectrum, and the radio device could receive the controlinformation and, based on the received control information, control atleast one UL radio transmission on the radio resources of the unlicensedfrequency spectrum.

FIG. 12 illustrates a processor-based implementation of a radio device1200 which may be used for implementing the above described concepts.For example, the structures as illustrated in FIG. 12 may be used forimplementing the above-mentioned UE 10.

As illustrated, the radio device 1200 may include a radio interface 1210for communicating with a wireless communication network, e.g., with anaccess node of the wireless communication network, such as theabove-mentioned access node 100. The radio interface 1210 may be usedfor receiving the above-mentioned control information, for performingthe above-mentioned UL radio transmissions, or for sending theabove-mentioned confirmation information. The radio interface 1210 mayfor example be based on the LTE radio technology.

Further, the radio device 1200 may include one or more processors 1250coupled to the radio interface 1210 and a memory 1260 coupled to theprocessor(s) 1250. By way of example, the radio interface 1110, theprocessor(s) 1250, and the memory 1260 could be coupled by one or moreinternal bus systems of the radio device 1200. The memory 1260 mayinclude a Read-Only-Memory (ROM), e.g., a flash ROM, a Random AccessMemory (RAM), e.g., a Dynamic RAM (DRAM) or Static RAM (SRAM), a massstorage, e.g., a hard disk or solid state disk, or the like. Asillustrated, the memory 1260 may include software 1270, firmware 1280,and/or control parameters 1290. The memory 1260 may include suitablyconfigured program code to be executed by the processor(s) 1250 so as toimplement the above-described functionalities of a radio device, such asexplained in connection with FIG. 8 .

It is to be understood that the structures as illustrated in FIG. 12 aremerely schematic and that the radio device 1200 may actually includefurther components which, for the sake of clarity, have not beenillustrated, e.g., further interfaces or processors. Also, it is to beunderstood that the memory 1260 may include further program code forimplementing known functionalities of a radio device, e.g., knownfunctionalities of a UE. According to some embodiments, also a computerprogram may be provided for implementing functionalities of the radiodevice 1200, e.g., in the form of a physical medium storing the programcode and/or other data to be stored in the memory 1260 or by making theprogram code available for download or by streaming.

FIG. 13 illustrates a processor-based implementation of a network node1300 which may be used for implementing the above described concepts.For example, the structures as illustrated in FIG. 13 may be used forimplementing an access node of the wireless communication network, suchas the above-mentioned access node 100.

As illustrated, the network node 1300 may include a radio interface 1310for communicating with radio devices, such as the above-mentioned UE 10and/or other UEs. The radio interface 1310 may be used for sending theabove-mentioned control information, for receiving the above-mentionedUL radio transmissions, or for receiving the above-mentionedconfirmation information. The radio interface 1310 may for example bebased on the LTE radio technology. Further, the network node 1300 mayinclude a network interface 1320 for communicating with other nodes of awireless communication network, e.g., access nodes or core networknodes.

Further, the network node 1300 may include one or more processors 1350coupled to the interfaces 1310, 1320 and a memory 1360 coupled to theprocessor(s) 1350. By way of example, the interfaces 1310, 1320, theprocessor(s) 1350, and the memory 1360 could be coupled by one or moreinternal bus systems of the network node 1300. The memory 1360 mayinclude a ROM, e.g., a flash ROM, a RAM, e.g., a DRAM or SRAM, a massstorage, e.g., a hard disk or solid state disk, or the like. Asillustrated, the memory 1360 may include software 1370, firmware 1380,and/or control parameters 1390. The memory 1360 may include suitablyconfigured program code to be executed by the processor(s) 1350 so as toimplement the above-described functionalities of a network node, such asexplained in connection with FIG. 10 .

It is to be understood that the structures as illustrated in FIG. 13 aremerely schematic and that the network node 1300 may actually includefurther components which, for the sake of clarity, have not beenillustrated, e.g., further interfaces or processors. Also, it is to beunderstood that the memory 1360 may include further program code forimplementing known functionalities of a network node, e.g., knownfunctionalities of an eNB of the LTE technology or similar access node.According to some embodiments, also a computer program may be providedfor implementing functionalities of the network node 1300, e.g., in theform of a physical medium storing the program code and/or other data tobe stored in the memory 1360 or by making the program code available fordownload or by streaming.

As can be seen, the concepts as described above may be used forefficiently controlling UL radio transmissions in an unlicensedfrequency spectrum. In particular, dynamic scheduling of individual ULradio transmissions can be avoided. Which may improve the performance inrelation to other radio technologies coexisting in the unlicensedfrequency spectrum.

It is to be understood that the examples and embodiments as explainedabove are merely illustrative and susceptible to various modifications.For example, the illustrated concepts may be applied in connection withvarious kinds of wireless communication technologies, without limitationto the above-mentioned examples of LTE, LTE LAA, or MuLTEfire. Further,the illustrated concepts may be applied in various kinds of radiodevices, including mobile phones, portable computing devices, machinetype communication devices, base stations, and relay stations. Moreover,it is to be understood that the above concepts may be implemented byusing correspondingly designed software to be executed by one or moreprocessors of an existing device, or by using dedicated device hardware.Further, it should be noted that the illustrated nodes or devices mayeach be implemented as a single device or as a system of multipleinteracting devices.

What is claimed is:
 1. A method, in a radio device, of controlling radiotransmission in a wireless communication network, the method comprisingthe radio device: receiving, from a node of the wireless communicationnetwork, control information for semi-persistent allocation of radioresources of an unlicensed frequency spectrum, wherein the controlinformation defines a first configuration applicable for a first uplinkcarrier and a second configuration applicable for a second uplinkcarrier, and wherein at least one of the first uplink carrier frequencyand the second uplink carrier frequency is from the unlicensed frequencyspectrum; sending, in a control element of a Medium Access Control (MAC)protocol, unlicensed spectrum semi-persistent scheduling grantconfirmation information to the node of the wireless communicationnetwork, the unlicensed spectrum semi-persistent scheduling grantconfirmation information consisting of at least one multi-bit value,wherein each bit of the multi-bit value comfirming individually for eachof the first uplink carrier and the second uplink carrier whethersemi-persistent allocation of radio resources is activated ordeactivated; and controlling, based on the control information, at leastone uplink radio transmission on the radio resources of the unlicensedfrequency spectrum.
 2. The method of claim 1, wherein the controlinformation indicates at least one maximum burst length allowed for theat least one uplink radio transmission on the radio resources of theunlicensed frequency spectrum.
 3. The method of claim 1, wherein thecontrol information indicates a configuration applicable formultiplexing different uplink radio transmissions on the radio resourcesof the unlicensed frequency spectrum.
 4. The method of claim 3, whereinthe control information indicates a configuration applicable formultiplexing different uplink control channel transmissions on the radioresources of the unlicensed frequency spectrum.
 5. The method of claim1, wherein the control information indicates one or more parameters of alisten-before-talk procedure to be applied by the radio device forcontrolling the at least one uplink radio transmission on the radioresources of the unlicensed frequency spectrum.
 6. The method of claim5, wherein the one or more parameters of a listen-before-talk procedurecomprise a backoff offset.
 7. The method of claim 6, wherein the backoffoffset differs from a backoff offset applied by one or more other radiodevices using the radio resources of the unlicensed frequency spectrum.8. The method of claim 1, wherein the control information indicates acyclic shift of a demodulation reference signal to be transmitted by theradio device on the radio resources of the unlicensed frequencyspectrum.
 9. The method of claim 8, wherein the cyclic shift of thedemodulation reference signal differs from a cyclic shift applied by oneor more other radio devices for transmission of a demodulation referencesignal on the radio resources of the unlicensed frequency spectrum. 10.The method of claim 1, wherein the control information requests theradio device to transmit one or more sounding reference signals on theradio resources of the unlicensed frequency spectrum.
 11. The method ofclaim 10, wherein the control information requests the radio device totransmit one or more sounding reference signals in a first burst of theat least one uplink radio transmission on the radio resources of theunlicensed frequency spectrum.
 12. The method of claim 1, wherein thecontrol information requests the radio device to transmit channel stateinformation on the radio resources of the unlicensed frequency spectrum.13. The method of claim 12, wherein the control information requests theradio device to transmit channel state information in a first burst ofthe at least one uplink radio transmission on the radio resources of theunlicensed frequency spectrum.
 14. The method of claim 1, wherein thecontrol information indicates a start symbol of an uplink data channelon the radio resources of the unlicensed frequency spectrum.
 15. Themethod of claim 14, wherein the control information indicates the startsymbol of the uplink data channel in a first burst of the at least oneuplink radio transmission on the radio resources of the unlicensedfrequency spectrum.
 16. The method of claim 1, wherein the controlinformation indicates an end symbol of an uplink data channel on theradio resources of the unlicensed frequency spectrum.
 17. The method ofclaim 16, wherein the control information indicates the end symbol ofthe uplink data channel in a first burst of the at least one uplinkradio transmission on the radio resources of the unlicensed frequencyspectrum.
 18. The method of claim 1, wherein the control informationindicates a modulation and coding scheme to be applied for the at leastone uplink radio transmission on the radio resources of the unlicensedfrequency spectrum.
 19. A method, in a node of a wireless communicationnetwork, of controlling radio transmission in a wireless communicationnetwork, the method comprising the node: semi-persistently allocatingradio resources of an unlicensed frequency spectrum to a radio device;sending, to the radio device, control information for controlling atleast one uplink radio transmission on the radio resources of theunlicensed frequency spectrum, wherein the control information defines afirst configuration applicable for a first uplink carrier and a secondconfiguration applicable for a second uplink carrier, and wherein atleast one of the first uplink carrier frequency and the second uplinkcarrier frequency is from the unlicensed frequency spectrum; andreceiving, in a control element of a Medium Access Control (MAC)protocol, unlicensed spectrum semi-persistent scheduling grantconfirmation information from the radio device, the unlicensed spectrumsemi-persistent scheduling grant confirmation information consisting ofat least one multi-bit value, wherein each bit of the multi-bit valueconfirming individually for each of the first uplink carrier and thesecond uplink carrier whether semi-persistent allocation of radioresources is activated or deactivated.
 20. A radio device for a wirelesscommunication network, the radio device comprising: a radio interfaceconfigured to perform at least one uplink radio transmission; processingcircuitry configured to cause the radio device to: receive, from a nodeof the wireless communication network and via the radio interface,control information for semi-persistent allocation of radio resources ofan unlicensed frequency spectrum, wherein the control informationdefines a first configuration applicable for a first uplink carrier anda second configuration applicable for a second uplink carrier, andwherein at least one of the first uplink carrier frequency and thesecond uplink carrier frequency is from the unlicensed frequencyspectrum; send, in a control element of a Medium Access Controlprotocol, unlicensed spectrum semi-persistent scheduling grantconfirmation information to the node of the wireless communicationnetwork, the unlicensed spectrum semi-persistent scheduling grantconfirmation information consisting of at least one multi-bit value,wherein each bit of the multi-bit value confirming individually for eachof the first uplink carrier and the second uplink carrier whethersemi-persistent allocation of radio resources is activated ordeactivated; and control, based on the control information, at least oneuplink radio transmission on the radio resources of the unlicensedfrequency spectrum.
 21. A node for a wireless communication network, thenode comprising: a radio interface configured for communication with aradio device; processing circuitry configured to cause the node to:semi-persistently allocate radio resources of an unlicensed frequencyspectrum to the radio device; send, to the radio device and via theradio interface, control information for controlling at least one uplinkradio transmission on the radio resources of the unlicensed frequencyspectrum, wherein the control information defines a first configurationapplicable for a first uplink carrier and a second configurationapplicable for a second uplink carrier, and wherein at least one of thefirst uplink carrier frequency and the second uplink carrier frequencyis from the unlicensed frequency spectrum; and receive, in a controlelement of a Medium Access Control (MAC) protocol, unlicensed spectrumsemi-persistent scheduling grant confirmation information from the radiodevice, the unlicensed spectrum semi-persistent scheduling grantconfirmation information consisting of at least one multi-bit value,wherein each bit of the multi-bit value confirming individually for eachof the first uplink carrier and the second uplink carrier whethersemi-persistent allocation of radio resources is activated ordeactivated.